Hydraulic table reciprocating mechanism



May 31, 1949. D. H. HCLMES 2,471,688

HYDRAULIC TABLE RECIPROCATING MECHANISM Filed June 15, '1945 2Sheets-Sheet 1 I [20 I36 I85 V I 7 V T I T 134 I] 124 I] 3 I23 v DONALDH. HOLMES 1 SEARCH ROOM 1949- D. H. HOLMES 2,471,688

HYDRAULIC TABLE RECIPROCATING MECHANISM Filed June 13, 1945 2Sheets-Sheet 2 F75. Z Y 1 3mm .DCJNALII H'. HOLMES M -mm I Patented May31, 1949 SEAEH 888% HYDRAULIC TABLE RECIPROCATING MECHANISM Donald H.Holmes, Worcester, Mass., assignor to Norton Company, Worcester, Mass.,at corporation of Massachusetts Application June 13, 1945, Serial No.599,184

Claims.

The invention relates to grinding machines, and more particularly to ahydraulically operated table reciprocating mechanism for a grindingmachine.

One object of the invention is to provide a simple and thoroughlypractical table reciprocating and reversing mechanism. Another object ofthe invention is to provide a table reversing mechanism with an improvedhydraulically operated dwell control mechanism. Another object of theinvention is to provide a table reversing mechanism with a hydraulicallyoperated variable dwell control mechanism whereby a va iable dwell maybe obtained at either or both ends of the reciprocatory stroke of thetable. A further object of the invention is to provide a hydraulicallycontrolled dwell control mechanism for delaying the shifting movement ofthe reversing valve into its reverse position. A further object of theinvention is to provide a hydraulically operated table reciprocatingmechanism with a hydraulically operated time delay control for the tablereversing valve to control the extent of dwell at each end of the tablestroke. Other objects will be in part obvious or in part pointed outhereinafter.

The invention accordingly consists in the features of construction,combinations of elements, and arrangements of parts, as will beexemplifled in the structure to be hereinafter described, and the scopeof the application of which will be indicated in the following claims.

The accompanying drawing, showing one of the various possibleembodiments of the mechanical features of this invention, in which Fig.1 illustrates a diagrammatic showing of a hydraulic control system ofthe improved table reciprocating mechanism.

Fig. 2 is a longitudinal sectional view, on an enlarged scale. of thetable control valve and the dwell control unit, together with connectingpiping, each being illustrated on the same relative scale.

As illustrated in the drawing, the machine embodying this inventioncomprises a base II! which supports a longitudinally reciprocable worktable II on the usual V-way and flat way (not shown) for a longitudinalreciprocatory movement relative to the base I0. A fluid operatedreciprocating mechanism is provided to reciprocate the table IIcomprising a fluid pressure cylinder I2 which is fixedly supported by apair of bracket end caps l3 and I4 which are fixedly mounted on theunder side of the table II. The cylinder l2 contains a pair of spacedpistons l5 and 16 which are connected by a pair of hollow piston rods 11and 18, respectively, with a pair of hollow brackets l9 and 20,respectively, mounted on opposite ends of the base 10.

The base It] is preferably formed as a box-like structure containing inits lower portion a reservoir 2| for the fluid pressure system. Fluid isdrawn from the reservoir 2! through a pipe 22 by means of a motor drivenfluid pressure pump 23. The pump 23 forces fluid under pressure througha pipe 24 to a table control or reversing valve 25. A pressure reliefvalve 26 is connected in the pipe line 24 to facilitate passing excessfluid under pressure through a pipe 21 into the reservoir 2! so as tomaintain a substantially uniform operating pressure within the hydraulicsystem.

The control valve 25 is a piston type valve having two parts which sliderelative to each other. A slidably mounted valve stem 28 is providedwith a pair of spaced valve pistons 29 and 30. A reduced cylindricalportion 3| of the valve stem 28 passes through a central aperture formedin a slidably mounted reversing valve member 32. The reversing valvemember 32 is provided with spaced integrally formed valve pistons 33, 34and 35. In the position of the valve parts as shown in Fig. 1, fluidunder pressure passing through the pipe 24 enters a passage 36 in thevalve casing and passes through a port 31 into a valve chamber 38located between the valve p stons 33 and 34 and passes out through aport 39 and a pipe 40 into a chamber 4| formed within the hollow bracketl9, through the hollow piston rod ll, into a cylinder chamber 42 formedat the left-hand end of the cylinder l2.

In this position of the parts, fluid within a cylinder chamber 43 formedat the right-hand end of the cylinder l2 may pass through the hollowpiston rod l8, through a chamber 44 formed within the bracket 20,through a pipe 45, through a port 45, into a valve chamber 41 locatedbetween the valve pistons 34 and 35, and out through exhaust ports 48and 48a and through a pipe 49 to a manually operable start and stopvalve 5|. The exhaust ports 48 and 48a are offset relative to each otherso that during the shifting movement of the valve piston 34, the exhaustof fluid from the cylinder into the exhaust pipe 49 is gradually cutoff.

The start and stop valve 5| is preferably a combined start-stop andspeed control valve and is preferably formed integral with the valve 25but for the sake of simplicity of illustration, it has been illustrateddiagrammatically in the drawing as a separate unit. The valve 5| ispreferably located in the exhaust side of the system so as to maintain auniform fluid pressure on the operating side of the main cylinder l2during the entire reciprocatory stroke of the cylinder I2 relative tothe pistons l5 and I6. An exhaust pipe 54 is operatively connected atthe right-hand end of the valve 5| to convey exhausting fluid back tothe reservoir 2|. The valve 5| comprises a valve stem 55 having formedintegrally therewith valve pistons 56 and 51. The control valve 5| isarranged so that it may be moved longitudinally from the full lineposition as shown in the drawings into the broken line position. Thevalve stem 55 is provided with an actuating knob 58 by means of whichthe valve may be rotarily adjusted. The righthand end face of the valvepiston 51 is formed as an angular plane face. By a rotary adjustment ofthe valve stem 55. the position of the angular end face of the piston 51may be adjusted so as to vary the aperture of the V-port 59 to thedesired and predetermined extent when the valve is in a startingposition and serves as a fine adjustment to cut off more or less of theexhaust of fluid from the system. thereby precisely to regulate thereciprocatory speed of the table II.

In order that the valve piston 51 may be maintained in the desiredadjusted position during starting and stopping of the table II, aserrated portion 60 is formed integral with the valve stem 55. Aspring-pressed arrow-pointed plunger 6| is supported by the casing ofthe valve 5| and is maintained in engagement with the serrated portion60 during the axial movement without changing the speed adjustmentthereof.

A manually operable start and stop lever 65 is pivotally supported on astud 66 which is in turn supported in a projecting boss 61 formedintegral with an apron 68 which is in turn fixedly supported on thefront of the machine base. The control lever 65 is provided with aclearance aperture 69 which surrounds a sleeve 10. The sleeve 10 isrotatably supported on the valve stem 55 and is provided with a pair ofdiametrically opposed grooves H which are engaged by a pair ofdiametrically opposed studs 12 (only one of which is illustrated in thedrawing) carried by the control lever 65. It will be readily apparentfrom the foregoing disclosure that when the control lever 65 ispositioned as indicated in full lines in the drawing, the V-port 59 isclosed so as to prevent movement of the table II.

When it is desired to start the reciprocatory movement of the table II,the control lever 65 is shifted in a counterclockwise direction intobroken line position 65a. This movement shifts the valve stem 55together with the valve pistons 56 and 51 toward the left into thebroken line position so that the valve piston 51 will wholly orpartially open the V-port 59 to allow a predetermined exhaust of fluidfrom the table cylinder I2 and thus control the speed of movement of thetable II.

When the valve 5| is in a closed position, such as shown in the drawing,it is desirable to provide a suitable by-pass whereby fluid may readilypass from the cylinder chamber 42 into the cylinder chamber 43 and viceversa to facilitate a manual traversing movement of the table II. A pipe80 is connected between the port 39 in the valve 25 and the valve 5|.Similarly, a pipe 8| is connected between the port 46 in the valve 25and the valve 5|. When the valve stem 55 is moved toward the right intoa table stop position (as shown in the drawing), a valve chamber 82located between the valve pistons 56 and 51 is positioned so that fluidmay readily pass between the pipes and 8| to facilitate a free passageof fluid between the cylinder chamber 42 and the cylinder chamber 43 ofthe table cylinder I2 so that the table may be readily movedlongitudinally without the necessity of overcoming fluid under pressurewithin the system.

A manually operable table traverse mechanism may be utilized such as,for example. that shown in the prior U. S. Patent No. 2,071,677, and maycomprise a manually operable hand wheel and a rack and gear mechanismfor moving the work supporting table II longitudinally. This mechanismis not considered to be a part of the present invention and consequentlyhas not been illustrated and described in detail. For further details ofthe manually operable table traversing mechanism, reference may be hadto the U. S. patent above referred to.

A table actuated mechanism is provided for initiating a shiftingmovement of the reversing valve 25 comprising a reversing lever 85 whichis mounted on the outer end of a rock shaft 86. The rock shaft 86 isjournalled in suitable bearings (not shown) formed in the apron 68. Ashort downwardly extending lever 81 is fixedly mounted on the inner endof the rock shaft 85. The lever 81 is provided with a stud 88 whichrides in a vertically extending groove 89 formed in the valve stem 28.The reversing lever 85 is provided with a rearwardly extending stud 90which is arranged in the path of a pair of adjustably mounted table dogs9| and 92. The table dogs 9| and 92 are adjustably supported in a T-slot 93 formed in the front edge of the'work supporting table II.

It is desirable to provide a dwell control mechanism whereby the worktable II may be stopped for a predetermined time interval at reversal soas to allow time to cause an infeeding movement of the grinding wheelbefore the table starts its movement in the reverse direction. Thisdwell control is preferably accomplished by retarding the shiftingmovement of the valve stem 28 and the reversing valve 32 of the controlvalve 25.

The valve 25 is provided with a valve chamber I00 located between thevalve pistons 29 and 33 which serves to facilitate a shifting movementof the reversing valve 32 in a manner to be hereinafter described. Itshould be noted that the differential effective areas of the pistons 29and 33 serve to aid in the reversal of the valve 25. A port |0loperatively connects the valve chamber I00 with a pipe I02 which is inturn connected with a fluid operated dwell control mechanism to behereinafter described. A port I03 connects fluid under pressure in hevalve passage 36 with the valve chamber I00 during the shifting movementthereof.

Similarly, the valve 25 is provided with a valve chamber I05 which islocated between the valve pistons 30 and 35, which serves to facilitatea shifting movement of the reversing valve 32 in a manner to behereinafter described. The differential efiective areas of the pistons30 and 35 also serve to aid in the reversal of the valve 25. A port I06operatively connects the valve chamber I05 with a pipe I01 which isoperatively connected with the dwell control mechanism to be hereinafterdescribed. A port I08 connects fluid under pressure in the valve passage36 with the '65 is moved into position 65a.

SEARCH ROOM 5 valve chamber I05 during the shifting movement thereof.

A fluid operated dwell control unit I I is shown on an enlarged scalerelative to the remainder of Fig. 1 to clarify the illustration of thedwell control unit H0. The unit H0 is provided which comprises a pistonI I I which is slidably mounted within a cylinder H2. The piston III isnormally urged in a downward direction by a compression spring I I3.When the valve stem 28 and the reversing valve 32 is moved toward theleft, fluid in the valve chamber I00 is forced through the port IOI, thepipe I02 and enters a cylinder chamber H4 to cause the piston III tomove upwardly against the compression of the spring II3 until a port H5is uncovered, which allows fluid under pressure within the cylinderchamber H4 to exhaust through a pipe H6 into a reservoir H1 within the(well control unit. The rate of upward movement of the piston III ispreferably controlled by regulating the exhaust of fluid from a cylinderchamber H8 formed at the upper end of the cylinder H2. Fluid exhaustingfrom the chamber H8 passes out through a pipe I I9 and through a needlevalve I which exhausts fluid through a pipe I2I into the reservoir H1.It will be readily apparent from the foregoing disclosure that byregulating the needle valve I20. the speed of movement of the piston IIImay be readily controlled so as to retard the movement of the reversingvalve 32 and thereby to regulate the period of dwell as desired.

As shown in Fig. l, the table I I will start movement toward the left assoon as the start lever This movement continues until the table dog 92engages the stud 90 on reversing lever and moves it in a counterclockwise direction, positively moving the valve stem 28 together withvalve pistons 2930 and reversing valve 32 toward the right (Fig. 1). Asthe reversing valve moves away from the lefthand end cap of the valvecasing, the capacity of the valve chamber I00 is increased suflicientlybefore port IOI is closed by valve piston 29 so that fluid within thechamber H4 may be exhausted by the downward movement of the piston H2under the influence of the released compression of spring H3. In orderto refill the cylinder chamber I I8, a passage I22 is connected with thereservoir II 1. A ball check valve I23 connects the pasage I22 with apassage I24 which is connected with the cylinder chamber H8. Suctioncreated by the downward movement of the piston III draws fluid throughthe ball check valve I23 to refill cylinder chamber H8 so that it isready for the next dwell control action.

The fluid operated dwell control unit I I0 is also provided with apiston I21 which is slidably mounted within a cylinder I28. The pistonI21 is normally urged in a downward direction by a compression springI29. Fluid under pressure passing through the pipe I01 enters a cylinderchamber I and causes the piston I21 to move upwardly against thecompression of the spring I 29 until a port I3I is uncovered, whichallows fluid under pressure Within the cylinder chamber I30 to exhaustthrough a pipe I32 into the reservoir H1 within the dwell control unit.The rate of upward movement of the piston I21 is preferably controlledby regulating the exhaust of fluid from a cylinder chamber I33 formed inthe upper end of the cylinder I28. Fluid exhausting from the cylinderchamber I33 passes out through a pipe I34 and through a needle valve I35which exhausts fluid through a pipe I36 into the reservoir H1. It willbe readily ap parent from the foregoing disclosure that by regulatingthe needle valve I35, the speed of movement of the piston I 21 may bereadily controlled so that the period of dwell may be regulated asdesired.

When the table is moved toward the right, the table dog 9I engages thestud 90 on the reversing lever and shifts the reversing lever 85 in aclockwise direction positively moving the valve stem together with valvepistons 29 -30 and reversing valve 32 toward the left (Fig. 1). As thereversing valve moves away from the righthand end cap of the valvecasing, the capacity of the valve chamber I05 is increased sufficientlybefore the port I06 is closed by valve piston 30 so that fluid withinthe chamber I31 may be exhausted by the downward movement of the pistonI21 under the influence of the released compression of spring I29. Inorder to refill the cylinder chamber I33, a passage I31 is connectedwith the reservoir H1. A ball check valve I38 connects the passage I31with a passage I39 which is connected with the cylinder chamber I33.Suction created by the downward movement of the piston I21 draws fluidthrough the ball check valve I38 to refill the cylinder chamber I33ready for the next dwell control action.

As illustrated in Fig. 2, the capacity of the valve chambers I00 and I95increases sufliciently during the shifting of the reversing valve toallow suflicient exhausting of fluid from the cylinder chambers H4 andI30 respectively, so that the pistons III and I21 may be moveddownwardly under the influence of the released compression of thesprings H3 and I 29 into engagement with the bottom of the cylinders II2 and I 28 respectively.

It will be readily apparent from the foregoing disclosure that theextent of dwell at each end of the table stroke may be readilycontrolled by the throttle valves I20 and I35, respectively. Thethrottle valves I20 and I35 respectively serve to control the speed ofupward movement of the pistons III and I2! during table reversal so asto delay the shifting movement of the reversing valve 25 into itsreverse position. After the pis tons II I and I2! move upwardly to apredetermined extent, namely, to a position whereby the ports I I5 andI3I are opened, the fluid may exhaust unrestricted through the pipe H6or the p pe I32 into the reservoir I I1.

The operation of the improved table reciprocating mechanism will bereadily apparent from the foregoing disclosure. Assuming all the partshave been previously adjusted and the table I I is traveling in thedirection of the arrow as shown in the drawings, that is, toward theleft, this movement will continue until the dog 92 engages the stud onthe reversing lever 85 and moves it in a counterclockwise direction.This movement of the reversing lever by actuation of the table dog 92serves to move the valve stem 28 which shifts both the valve pistons 29and 30 and also the reversing valve 32 until the reversing valve piston34 closes the exhaust ports 48 and 4811, thus stopping the tablemovement. During this movement of the valve parts, the capacity of thevalve chamber I00 increases so as to allow the released compression ofthe spring H3 to move piston III into its lower position (Fig. 2),exhausting fluid from the chamber H4 through the pipe I02 and the portIOI into expanded valve chamber I00. This takes place before the valvepiston 29 closes the port IIlI The admission of fluid under pressure tothe cylinder chamber I30 causes an upward movement of the piston I21 ata rate con trolled by the needle valve I35. During this movement, theparts of the valve 25 move at a slow controlled rate as governed by thedwell control unit. This condition prevails until the piston I21 movesupwardly a suflicient distance to open the port I BI and thereby toallow unrestricted exhaust of fluid through the pipe I32. At this timefluid under pressure in the passage 36 of the valve 25 passes throughthe port I03 into the valve chamber I08 and due to the differential inpiston reas causes the reversing valve 32 to move rap dly toward theright to throw it into a reverse position. In the reverse position,fluid under pressure within the chamber 32 of the valve 25 may passthrough the valve chamber 61 and out through the port 45, the pipe 45,the passage 44, the hollow piston rod I8, into the cylinder chamber 43to start the movement of the table II toward the right.

The movement of the table continues toward the right until the reversingdog 9| engages the stud 93 which is now in position 90a and shifts thereversing lever 85 from the broken line position 85a in acounterclockwise direction, as shown in the drawings. This movement ofthe reversing lever 85 serves to move both the valve stem 28 and thereversing valve 32 toward the left until the reversing valve piston 34again closes the ports 48 and 48a, thus preventing further exhaust offluid from the cylinder chamber 42. In this position of the reversingvalve, fluid within the chamber 36 of the valve 25 passes through theport I63, the pipe I02, into the dwell control valve cylinder chamberII4 to move the dwell control piston III upwardly. The speed of theupward movement of the piston III is governed by the needle valve I20.The upward movement of the piston IlI continues until the piston IIIreaches the position illustrated in the drawings to uncover the port IIso as to allow a substantially unrestricted exhaust of fluid through thepipe IIG into the reservoir II'I.

When the reversing valve parts reach the latter position in theirmovement toward the left, fluid within the valve passage 36 may passthrough the port I68 into the valve chamber I05 and due to thedifferential areas of the pistons 35 and 30, serves to cause thereversing valve 32 to move rapidly toward the left so as to admit fluidunder pressure through the port 39, the pipe 40, the passage 4 I, thehollow piston rod I1, into the cylinder chamber 42 to start the movementof the table II toward the left.

It will be readily apparent from the foregoing disclosure that theupward movement of the pistons III and I21, as regulated by the needlevalves I and I35 respectively, serves to provide an adjustable dwell ateach end of the table stroke by retarding the shifting of the reversingvalve into a reverse position for a predetermined but adjustable timeinterval. The dwell at either end of the table stroke may be readilyvaried by manipulation of the needle valves I20 and I35.

It will thus be seen that there has been provided by this inventionapparatus in which the various objects hereinabove set forth togetherwith many thoroughly practical advantages are successfully achieved. Asmany possible embodiments may be made of the above invention and as manychanges might be made in the embodiment above set forth, it is to beunderstood that all matter hereinbefore set forth or shown in the ac- 8companying drawings is to be interpreted as illustrative and not in alimiting sense.

I claim:

1. In a hydraulically operated table reciprocating mechanism, alongitudinally reciprocable table, a piston and cylinder therefor, asource of fluid under pressure, a piston type reversing valve comprisinga slidably mounted valve member having a pair of spaced valve pistonsthereon, a reversing valve slidably supported on said member having aplurality of spaced integrally formed pistons, a valve chamber formed ateach end of the reversing valve between the reversing valve and saidspaced pistons respectively, table actuated means to shift the valvemember and the reversing valve to shift the reversing valve to a centralposition so as to cut off exhaust of fluid from the table cylinder,means to admit fluid under pressure to one of said valve chambers toshift the reversing valve into a reverse position, and means to providea predetermined back pressure in the other valve chamber to prevent theshifting of the reversing valve into a reverse position for apredetermined but adjustable period of dwell during reversal of thetable.

2. In a hydraulically operated table reciprocating mechanism, alongitudinally reciprocable table, a piston and cylinder to reciprocatesaid table, a source of fluid under pressure, a piston type reversingvalve comp a s ably mounted valve member having a pair of spaced pistonsthereon, a reversing valve slidably supported on said member having aplurality of spaced integrally formed pistons, a valve chamber formed ateach end of the reversing valve between the reversing valve and saidspaced pistons, adjustable table dogs, a reversing lever actuatedthereby to shift said valve member and reversing valve to shift thereversing valve to a central position so as to cut off exhaust of fluidfrom the table cylinder, means to admit fluid under pressure to one ofsaid end chambers to apply pressure tending to shift said valve into areverse position, and a dwell control device arranged to provide a backpressure in the other end chamber for a predetermined but adjustabletime interval to prevent shifting of the reverse valve into a reverseposition until after a predetermined period of dwell.

3. In a hydraulically operated table reciprocating mechanism, alongitudinally reciprocable table, a piston and cylinder to reciprocatesaid table, a source of fluid under pressure, a piston type reversingvalve comprising a slidably mounted valve member having a pair of spacedpistons thereon, a reversing valve slidably supported on said memberhaving a plurality of spaced integrally formed pistons, a valve chamberformed at each end of the reversing valve between the reversing valveand said spaced pistons, adjustable table dogs, a reversillg leveractuated thereby to shift said valve member and reversing valve to shiftthe reversing valve to a central position so as to cut off exhaust offluid from the table cylinder, means to admit fluid under pressure toone of said end chambers to apply pressure tending to shift said valveinto a reversed position, an independent dwell control device for eachend of the table stroke, and independent connections between said valvechambers and said devices, one of said devices being opera.- tive ateach reversal of said valve to delay shifting of said reversing valveinto a reverse position for a predetermined time interval.

4. In a hydraulically operated table recipro- SEARCH R0 eatingmechanism, a longitudinally reciprocable table, a piston and cylinder toreciprocate said table, a source of fluid under pressure, a piston typereversing valve comprising a slidably mounted valve member having a pairof spaced pistons thereon, a reversing valve slidably supported on saidmember having a plurality of spaced integrally formed pistons, a valvechamber formed at each end of the reversing valve between the reversingvalve and said spaced pistons, adjustable table does, a reversing leveractuated thereby to shift said valve member and reversing valve to shiftthe reversing valve to a central position so as to cut off exhaust offluid from the table cylinder, means to admit fluid under pressure toone of said end chambers to apply pressure tending to shift said valveinto reverse position, a hydraulic dwell control device including a.hydraulic piston and cylinder, a compression spring normally to maintainsaid piston in a lower position, fluid connections between the lower endof said latter cylinder and one of said valve chambers whereby fluidunder pressure in said valve chamber passes into the lower end of saidlatter cylinder to raise said piston against the compression of saidspring, a throttle valve to control the speed of movement of saidpiston. and a port opened after the piston has moved to a predeterminedposition to facilitate shifting of the reversing valve into a reverseposition after a predetermined period of dwell.

5. In a hydraulically operated table reciprocating mechanism, alongitudinally reciprocable table, a piston and cylinder to reciprocatesaid table, a source of fluid under pressure, a piston type reversingvalve comprising a slidably 10 mounted valve member having a pair ofspaced pistons thereon, a reversing valve slidably supported on saidmember having a plurality of spaced integrally formed pistons, a valvechamber formed at each end of the reversing valve between the reversingvalve and said spaced pistons, adjustable table dogs, a reversing leveractuated thereby to shift said valve member and reversing valve to shiftthe reversing valve to a central position so as to cut off exhaust offluid from the table cylinder, means to admit fluid under pressure toone of said chambers to apply pressure tending to shift said valve intoa reverse position, an independent hydraulically operated dwell controlunit operatively connected with each of said valve chambers, eachincluding a piston and cylinder, fluid connections between the lower endof each of said valves and said valve members respectively, anindependent throttle valve to control the exhaust of fluid from theother end of each of said cylinders, a port opened after a predeterminedmove of said latter pistons to allow unrestricted exhaust of fluid fromsaid latter cylinders, said throttle valves being arranged to provide apredetermined adjustable dwell at each end of the table stroke.

DONALD H. HOLMES.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,290,832 Flygare July 21, 19422,365,811 Fiygare Dec. 26, 1944

